688
FXUS65 KBYZ 290754
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
154 AM MDT FRI AUG 29 2025
KEY MESSAGES
- SCATTERED SHOWERS AND THUNDERSTORMS CONTINUE ACROSS THE REGION
THROUGH SATURDAY, WITH LOCALLY HEAVY RAINFALL POSSIBLE. GREATEST
POTENTIAL FOR HEAVY RAIN WILL BE EAST OF THE WESTERN FOOTHILLS.
- THERE IS A LOW RISK OF FLASH FLOODING IN AND NEAR AREA BURN
SCARS TODAY.
- WARMER AND DRY SUNDAY AND MONDAY.
- TRENDING COOLER AND MAINLY DRY TUESDAY INTO THURSDAY.
DISCUSSION
THROUGH SATURDAY NIGHT...
A COUPLE MID LEVEL CIRCULATIONS NOTED ON SATELLITE. ONE IS IN
NORTH CENTRAL MT AND THE OTHER IN THE FAR NE CORNER OF WY, THE
LATTER OF WHICH IS PRODUCING AN AREA OF SHOWERS IN SOUTHEAST MT.
SCATTERED LIGHT SHOWERS AND SPRINKLES EXIST ELSEWHERE (STRONGER
FORCING HAS SHIFTED NORTH AND EAST). WE REMAIN IN A REGION OF
ANOMALOUSLY HIGH PRECIPITABLE WATERS AND LIGHT WINDS ALOFT, SO
ALL ACTIVITY IS EVOLVING SLOWLY AND WILL CONTINUE TO DO SO.
ATMOSPHERIC MOISTURE WILL BEGIN TO DECREASE SLOWLY TODAY AS W-NW
WINDS DEVELOP OVER THE WEST HALF OF OUR FORECAST AREA. GIVEN THIS,
GREATEST POTENTIAL FOR SHOWERS CAPABLE OF PRODUCING LOCALLY HEAVY
RAIN TODAY WILL SHIFT EAST OF THE WESTERN FOOTHILLS. WILL ALSO
NEED TO WATCH FOR A NW-SE ORIENTED CONVERGENT AXIS FROM ROUGHLY
WHEATLAND TO CARTER COUNTIES, WHICH COULD BE A FOCUS OF HEAVIER
SHOWERS AS WELL WHEN WE GET TO THE PEAK HEATING HOURS. THERE WILL
OF COURSE BE SOME EMBEDDED T-STORMS BUT THEY SHOULD REMAIN WEAK
AND CHAOTIC. ISOLATED (WEST) TO SCATTERED (CENTRAL & EAST) SHOWERS
WILL CONTINUE THRU TONIGHT.
THE WEST WILL SEE CONTINUED DRYING SATURDAY AS AN UPPER LEVEL
RIDGE BEGINS TO EXERT ITSELF OVER THE WEST HALF OF THE STATE.
THUS, GREATEST CHANCES OF WETTING RAIN WILL BE OVER THE EAST AND
PERHAPS SOUTHERN UPSLOPE AREAS AS NW WINDS DEEPEN A BIT. THAT
SAID, THERE SHOULD BE ENOUGH BOUNDARY LAYER MOISTURE TO POP SOME
DIURNAL SHOWERS EVEN IN OUR WEST. ONCE AGAIN, ANY AFTERNOON AND
EARLY EVENING T-STORMS WILL REMAIN NON-SEVERE AS BULK SHEAR
REMAINS AT 15 KNOTS OR LESS. MIXED DEW POINTS MAY FALL TO AS LOW
AS THE LOWER 40S ALONG THE WESTERN FOOTHILLS TOMORROW AFTERNOON, A
SIGN OF CHANGES COMING. LOOK FOR MORE WIDESPREAD DRYING SATURDAY
NIGHT.
TEMPS WILL REMAIN JUST A BIT COOLER THAN NORMAL THE NEXT TWO DAYS,
WITH HIGHS IN THE MID 70S TO LOWER 80S. FINALLY, WITH A BETTER
CHANCE OF PARTIAL CLEARING, WE COULD SEE LOCALIZED FOG LATE
TONIGHT AND EARLY SATURDAY. SOMETHING TO MONITOR.
JKL
SUNDAY THROUGH THURSDAY...
SUNDAY AND MONDAY CONTINUE TO LOOK WARM AND DRY AS THE AMPLIFIED
RIDGE OVER THE WEST COAST NUDGES INTO THE AREA, PUSHING HIGHS INTO
THE MID TO UPPER 80S. THE CHANGE THIS FORECAST RUN IS THAT
THE CANADIAN COLD FRONT ADVERTISED FOR EARLY WEDNESDAY LOOKS TO
ARRIVE SOONER, POSSIBLY AS EARLY AS TUESDAY MORNING. THE NBM
REASONABLE TEMPERATURE RANGE SPREAD FOR BILLINGS ON TUESDAY
AFTERNOON IS NOW 14 DEGREES (72 TO 86 DEG) SHOWING THAT SOME BUT
NOT ALL MODEL ITERATIONS ARE ON BOARD WITH THE EARLY FRONTAL
ARRIVAL. THAT SAID THE SPREAD FOR TUESDAY IN PREVIOUS RUNS WAS
SMALL AND IN THE MID TO UPPER 80S SO THIS IS A SIGNIFICANT SHIFT
TO THE COLDER SIDE.
TEMPERATURES WEDNESDAY CONTINUE TO TREND COOLER IN THE NBM
ENSEMBLES WITH HIGHS ADVERTISED FROM THE UPPER 60S EAST TO THE
UPPER 70S IN THE WEST. HOWEVER, THERE IS STILL A GOOD DEAL OF
UNCERTAINTY WITH HOW COOL THIS SYSTEM WILL BE OVER OUR AREA. A
REASONABLE RANGE FROM 64 TO 78 DEGREES EXISTS FOR HIGHS IN
BILLINGS FOR EXAMPLE. THIS IS A BROAD SPREAD BUT LOOKING CLOSER
THE MEDIAN IS SITTING AT 68 DEGREES, SO SOME VERY WARM OUTLIER
ENSEMBLE MEMBERS ARE SKEWING THE RANGE ON THE HIGH SIDE AND MORE
MEMBERS ARE CLUSTERED IN THE 60S. THE DETERMINISTIC NBM, WHICH
POPULATES THE GRIDDED FORECAST, IS SHOWING 75 DEGREES FOR BILLINGS
WEDNESDAY, WELL ABOVE THE ENSEMBLE MEDIAN. THINKING THIS IS
MAINLY DUE TO A LATENCY BIAS BUILT INTO THE DETERMINISTIC NBM AND
THAT THIS WARM BIAS WILL DECREASE AS THE FORECAST MOVES FORWARD,
IF CURRENT MODEL TRENDS CONTINUE. MODEST WARMING IS EXPECTED ON
THURSDAY WITH 70S TO LOWER 80S FORECAST. FOR REFERENCE, NORMAL
HIGHS FOR THE END OF AUGUST ARE IN THE LOWER 80S.
PRECIPITATION POTENTIAL WITH THIS SYSTEM IS MODEST TO LOW AS
PACIFIC MOISTURE IS CUTOFF BY THE WESTERN RIDGE AND THE NORTHERLY
LOW LEVEL WINDS BLOCK PLAINS MOISTURE FROM MAKING IT INTO OUR
AREA. CHAMBERS
AVIATION
MONSOONAL MOISTURE WILL CONTINUE OVER THE AREA THROUGH TONIGHT.
SCATTERED WEAK SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE
OVERNIGHT TONIGHT INTO THE MORNING HOURS. SCATTERED AFTERNOON
CONVECTION WILL BE STRONGER WITH LOCALLY HEAVY RAINFALL POSSIBLE.
MVFR CONDITIONS WILL BE POSSIBLE NEAR PRECIPITATION AREAS MAINLY
DUE TO POOR VISIBILITIES. OVERNIGHT AND EARLY MORNING PATCHY FOG
IS POSSIBLE WITH LOCAL IFR OR LOWER CONDITIONS POSSIBLE. OTHERWISE
VFR CONDITIONS WILL PREVAIL WITH PERSISTENT MID LEVEL CEILINGS IN
PLACE. CHAMBERS
PRELIMINARY POINT TEMP/POPS
TDY SAT SUN MON TUE WED THU
-------------------------------------------------------
BIL 079 057/081 055/088 057/088 058/083 053/078 050/081
5/T 32/T 00/U 00/U 01/B 21/U 00/U
LVM 078 047/080 048/085 049/086 050/083 047/080 046/082
2/T 22/W 00/U 00/U 01/U 11/U 10/B
HDN 079 055/079 052/087 053/088 054/083 050/078 047/081
6/T 43/T 10/U 00/U 01/B 21/B 00/U
MLS 079 059/078 056/086 055/086 056/081 050/073 046/078
4/T 43/T 10/U 00/U 11/B 21/U 00/U
4BQ 073 057/074 053/081 055/084 057/081 050/072 047/075
5/T 54/T 20/U 00/U 01/B 21/B 10/U
BHK 077 054/075 052/081 053/084 053/078 044/069 042/075
2/T 34/T 11/U 00/U 11/B 21/B 00/U
SHR 076 050/076 048/083 050/084 051/083 048/075 044/078
7/T 45/T 11/U 00/U 01/U 22/W 10/U
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
WEATHER.GOV/BILLINGS
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